THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE II. VOL. VI. 



No. IV.— APRIL, 1879. 



OZRIGKEZCsrJLILi .A. IK, TIC LIES. 



I. — On some Fish Exuvi-as from the Chalk, generally referred 

 to Dercetis elongatus, Ag. ; and on a New Species of Fossil 

 Annelide, Terebella Lewesiensis. 



By William Davies, F.G.S., 

 of the British Museum. 



A NOT uncommon fossil of the Chalk, in both the upper and lower 

 divisions, is an elongated, and more or less undulating body, 

 composed of the scales and bones of fishes confusedly mingled one 

 with another, and known to the quarrymen as " Petrified Eels." 

 Dr. Mantell was the first to discover and describe these singular 

 objects ; he says, " A long cylindrical fish, of which neither the 

 fins nor the extremities have been discovered, is one of the most 

 frequent, but most imperfect of the Sussex ichthyolites. The 

 specimens are of a subcylindrical form, rather flattened by com- 

 pression, from six inches to two feet in length, and about one inch 

 wide. They occur abundantly in the Upper Chalk, and occasionally 

 in the siliceous nodules. They are, for the most part, perfectly 

 straight ; but some specimens are undulated, as if the fish had been 

 suddenly enveloped in the Chalk while in a state of motion. The 

 surface is covered with small delicate smooth scales, confusedly 

 mixed together ; not one instance having been noticed in which they 

 are disposed with any degree of regularity." 



" Until more illustrative specimens shall be discovered, our con- 

 jectures concerning the recent animal must be vague and unsatisfac- 

 tory. That the remains in question are referable to a fish of the Order 

 Apodes cannot, however, be questioned, and they certainly appear to 

 be more intimately related to the genus Murcena, than to any other 

 with which we are acquainted." 1 And he accordingly names them 

 Murosna? Lewesiensis. In subsequent works 2 he refers them to 

 Dercetis elongatus, Agassiz ; probably from two small fragments in 

 his collection, and figured in the work above quoted (tab. 34, figs. 

 10 and 11), regarding which specimens he says fig. 11 "is the only 

 example " of Murcena Lewesiensis " that retains the slightest indica- 

 tion of a fin," whilst that of fig. 10 " shows vestiges of the tail, 

 and of one fin, but no conjecture can be formed of the genus of the 



1 Fossils of the South Downs, 1822, p. 232, tah. 34, fig. 10, tah. 40, fig. 2. 



2 Medals of Creation, 1844, vol. ii. p. 658; Petrifactions and their Teachings. 

 1851, p. 438. 



DECADE II. — VOL. VI. NO. IV. 10 



